A conventional vehicle lamp is disclosed in U.S. Pat. No. 7,736,036. FIGS. 2 and 5 of U.S. Pat. No. 7,736,036 are referred to in the following description.
The conventional vehicle lamp includes a projector lens 12, a light emitting element 14, and a reflector 16. The projector lens 12 defines an optical axis (Ax) extending in a front-rear direction, and includes front and rear side surfaces 12a, 12b spaced apart along the optical axis (Ax). The light emitting element 14 is proximal to a rear focal point (F) of the projector lens 12. The reflector 16 reflects light from the light emitting element 14. The front side surface 12a is formed with a plurality of lens elements 12As, 12Bs extending substantially in a horizontal direction and spaced apart vertically. An external surface of each of the lens elements 12As, 12Bs has a waveform shape. A light distribution pattern formed by the light which radiates from the conventional vehicle lamp has a cutoff line.
The lens elements 12As, 12Bs are for diffracting light emitted by the light emitting element 14 when the light passes through the projector lens 12 such that light is diffracted to above the cutoff line, reducing discomfort for drivers in an oncoming vehicle.
However, the positions and angles of the lens elements 12As, 12Bs must be precisely controlled so that the diffracted light converge, otherwise the light may be over-diffracted, leading to an increase in brightness above the cutoff line or a decrease in brightness below the cutoff line, causing discomfort to the oncoming driver or producing insufficient lighting for the driver of the vehicle.